Pressure arming device

ABSTRACT

5. AN ARMING DEVICE FOR UNDERWATER MINES COMPRISING A SOURCE OF ELECTRICAL POWER, A MINE POWER SUPPLY CIRCUIT, A NORMALLY OPEN CONTROL CIRCUIT, RELAY MEANS RESPONSIVE TO CLOSURE OF SAID CONTROL CIRCUIT TO CONNECT TO SAID POWER CIRCUIT TO SAID SOURCE, MEANS RESPONSIVE TO A DROP IN PRESSURE TO CLOSE SAID CONTROL CIRCUIT, A FIRST TIMING MEANS OPERABLE TO OPEN SAID POWER CIRCUIT AFTER A GIVEN TIME AND A SECOND TIMING MEANS OPERABLE UPON OPENING OF THE POWER CIRCUIT TO BLOCK OPERATION OF THE CONTROL CIRCUIT FOR A GIVEN TIME. D R A W I N G

Feb. 13, 1973 c, HAYES ETAL 3,715,982

PRESSURE ARMING DEVICE Filed Dec. 3. 1946 2 Sheets-Sheet l HARVEY C. HAYES HORACE M. TRENT allow;

Feb. 13, 1973 H. c. HAYES ETAL PRESSURE ARMING DEVICE 2 Sheets-Sheet 2 Filed Dec. 5, 1946 l l l l l MINE BATTERIES PRESSURE RELAY DEVIC E SYSTEM SENSING DEVICE AN D AMPLIFIER T N Y E AR H GM YE EC VA RR A0 HH 3,7l5,%2 Patented Feb. 13, 1973 3,715,982 PRESSURE ARR/ENG DEVKCE Harvey '8. Hayes, Washington, l).., and Horace M.

Trent, Alexandria, Va. (both Naval Research Laboratory, Washington, 9.6. 20020) Fiied Dec. 3, 1946, Ser. No. 713,730 int. Ql. F42h 21/38; F42c 13/00 U5. Cl. 102-18 6 Claims The present invention relates in general to underwater mines and more particularly to arming devices therefor.

An important requirement in the art of mining waterways is the production of a mine that will give an enemy great difiiculty and cause great delay in devising means for sweeping either in the literal sense of mechanical sweeping as with towed gathering cables or cable cutters, or in the more general sense of rendering the mines ineffective in any way as by bringing about their detonation from a distance.

Underwater mines are usually designed for placement on or near the bottom of a Waterway and are provided with sensing means responsive to sound, light, a magentic field or other phenomena accompanying the arrival of a ship within the zone of effectiveness of the mine. The sensing means responds to close an electric detonating circuit usually through a suitable amplifier.

Such mines are difficult to sweep mechanically because of their placement on or near, the bottom of the waterway, but may be detonated from a safe distance by production of a strong field of influence of suitable characteristics to create or simulate the condition to which the mines sensing means is designed to respond, for example a strong earn of underwater sound waves, for an acoustic mine.

Mines, like various other kinds of explosive devices are usually designed to remain ineffective or nonresponsive until ready for use when they are made ready or responsive. This making ready is termed arming, and when so made ready the mine is said to be armed.

An object of the present invention is the provision of an arming device for rendering an underwater mine of the acoustic, magnetic or other noncontact type, extremely difficult to detonate by means other than its intended quarry.

Another object is to provide a mine arming device responsive only to the presence of a ship of over a given size or displacement.

A further object is to provide a mine responsive to the presence of ships of over a given size or displacement together with means for rendering the device nonresponsive to natural phenomena resembling the movement of a ship thereover.

Another object is to provide a mine control device responsive to the drop in pressure near the bottom of a body of water, produced by the passage of a ship or like object thereover.

Various other objects and advantages of the invention will become apparent from a perusal of the following specification and the drawings accompanying the same.

In the drawings:

FIG. 1 is a longitudinal sectional view, mainly diagrammatic, of an exemplary embodiment of the pressure responsive, control device of the arming system.

FIG. 2 is a schematic diagram of the control circuit.

FIG. 3 is a diagram showing arrangement of the component elements of the pressure arming system in a mine casing.

The principle of operation of the invention is based upon the fact that there are hydrostatic pressure variations produced at the bottom of a waterway upon the passage of a ship thereover. It has been found experimentally that there are regions of increased pressure at the bottom of a waterway ahead and astern of a surface ship and a decreased pressure region between the first two regions. The maximum negative pressure variation from the mean is greater than either of the positive variations and it is the former variation that is utilized in the present invention.

FIG. 1 shows mainly in diagrammatic form, a preferred mechanical embodiment of the pressure responsive device. It comprises a rigid walled air chamber 10 and a collapsible, or flexible-walled air chamber 11, the two chambers separated by a flexible diaphragm 12 movable in response to a differential of pressure between the two chambers for movement of a contact element 13 wth respect to a complementary contact element 14. Motion is transmitted from the diaphragm to the contact element 13 through a stylus element 15 secured at the center of the diaphragm and projecting into the contact-housing chamber 10 where it engages an actuating arm 16 for the contact 13, both fixed to a shaft 17 biased in a counterclockwise direction by a hair spring is anchored on an insulating block 19. The stylus passes through an opening 20 in the bottom wall 21 of the chamber 19, the lower face of which wall serves as a mounting foundation for the diaphragm and is provided with a recessed surface portion 22 to serve as a diaphragm stop to limit the upward movement of the diaphragm.

Because the device is used under water it should be properly sealed against leakage of water into the chambers particularly the contact-housing chamber and to this end the latter is sealed by a cover plate 23 bolted in place with an intervening soft rubber gasket 24. The flexible chamber element 11 is housed in a casing 27, the latter in continuous communication with the surrounding body of water through at protecting screen 25 and the opening 26. The diaphragm i2 is thus sealed from direct contact with the water by the flexible chamber element 11 of rubber or the like sealed about the diaphragm and the relatively large intervening body of air within the chamber 11 by the thickened flange portion 28 clamped between the flanges 29 and 30 which flanges join the chamber element 10 and casing 27 through the aid of clamping bolts 31. The diaphragm is mounted independently of the joint between chamber element 11 and casing 27 by means of the bottom diaphragm plate 32 closing the recess in the chamber wall 21 and clamping the diaphragm in place at the peripheral margin of the latter with an intervening gasket ring 33.

To obtain pressure equilibrium between the two chambers and maintain such condition except for the relatively high rates of change to which the device is intended to respond, a bleed duct 34 is provided in a thickened portion of the side wall of the upper chamber for maintaining a slow leak connection between the two chambers. Resistance to air flow through the duct is regulated by the regulating screw 35 threaded into the chamber wall in intersecting relation with the bleed duct. Thus, during descent of the device to its operating depth. equalization takes place through passage of air from within the flexible sack in the lower chamber, through the duct 34 to the upper chamber. This passage of air continues after the device reaches its operating depth and until pressure equilibrium obtains.

Because the pressure variations to which the device is intended to respond lessen in amplitude with depth, it is desirabie that means be provided for automatically increasing the sensitivity of the device with depth in order that in relatively shallow water it will not respond to light craft against which protection is not considered important, and will be sufiiciently sensitive to respond to heavier craft at considerable depths. To this end the contact element 13 is comprised of a piece of conducting wire. preferably of platinum or the like, extending away from its pivotal shaft 17 in a curve to present a contacting surface of considerable lineal extent, while the contact element 14 is arranged to move along an are 36 eccentric to the arcform of contact 13 so as to vary its distance from the contact 13. The contact 14 is comprised of a piece f conducting wire, preferably of platinum or the like, carried by the shaft 37 and having its free or contacting end bent at a right angle so as to extend across the contact 13. Movement of the contact 14 in response to depth below the surface of the waterway is effected by a Bourdontube gauge element 38 coupled to the shaft 37 through a radial arm 39, link 40 and arm 41 fixed to the shaft 37. A hair spring 42 anchored on an insulating block 43 maintains a biasing torque on the shaft 37 in a clockwise direction. The gauge element is arranged so that reduction in diameter or winding up of its helix in response to an increase in pressure in the chamber 10 due to increase in underwater depth of the device will swing the radial arm 3) in a counteclockwise direction against the tension of hair spring 42 to bring the contact element 14- closer to the contact 13. Thus the pivotal mounting of the contact element 14 on the shaft 37 constitutes calibrating means for varying the sensitivity of the fast acting contact moving pressure responsive means consisting of the diaphragm l2 and its linkage with the contact element 13. To maintain the interior of the Bourdon gauge element at a substantially constant reference pressure say approximately atmospheric pressure, the gauge is provided with an extension tube 43 extended out through the gasket 24 and cover plate 23 for communication with any suitable sealed space of several times the volume of the Bourdon tube, within the casing of the mine with which the pressure vice is used. By suitable formation of curvature of the contact 13, the change in spacing between the contacts with depth may be made to effectively follow the change in pressure variation to which the device is desired to respond at different depths. Control circuit conductors 44 and 45 extend electrical connection from the contacts 13 and 14 to a suitable relay system for connecting a battery power supply to the mines sensing and amplifying means (not shown) to arm the mine. Any known or other form of relay system capable of effectively filtering out relatively rapidly recurring closures of its input circuit may be used. By the term effectively filtering out is meant the rendering of such recurring closures ineffective to close the relay output circuit or complete connection of battery power supply to the mines sensing and amplifying means.

e form of such a discriminating relay circuit found workable in the present combination for compensating for high wave effects and conserving batteries during stormy weather, is shown diagrammatically in FIG. 2. This comprises a relay tube V of the cold cathode, gas type having an input dropping resistance R fed from the B-battery B435 of the battery power supply, through the control circuit conductors 44-45 in series with a time delay, capacity-resistance blocking circuit composed of condenser C and resistance R Voltage drop across resistors R is applied to the grid of the tube V through grid limiting resistance R The function of the blocking circuit C-R is to block off current supply to the dropping resistance R after the condenser C becomes charged and until the source of current supply has been disconnected for a period of time determined by resistor R controlling the discharge rate of the condenser.

The tube V draws its plate current from the B battery through the energizing coil of an electromagnetic relay 46 having a pair of normally open contacts 47 and 48 operable to connect the positive terminals of the B and A batteries designated 3-135 and A, respectively, to the supply conductors 49 and 50, respectively, leading to a suitable amplifier and sensing device not shown and which may be any known or other suitable sensing and amplifying device for effecting detonation of the mine in response to the presence of a ship, for example, an acoustic sensing device responsive to propeller noise. The B-supply conductor 49 while thus con ected supplies B- atter potential to the blocking circuit to maintain the condenser C charged during energization of the relay, while the current from the A-supply conductor feeds a heating resistance R, for actuating a normally closed thermostatic time delay switch 51 of the bi-metallic strip type in the cathode circuit of the tube for opening the cathode circuit to quench the tube after a predetermined time interval of say about twenty seconds.

In use the pressure arming system may be installed in any type of underwater mine having a sensing device operable through an amplifier to effect detonation of the mine. FIG. 3, indicates diagrammatically the system installed in a mine of the type dropped from aircraft. Here the various component units are indicated as installed in the tail-end chamber of the mine casing. Essentially, it is sufficient only that the water inlet opening 26 of the pressure device have communication, through suitable conduit connection such as the tube 52, with the surrounding body of water and that the extension tube 43 of the Bourdon pressure gauge communicate with the sealed interior space in the tail-end compartment of th mine.

In operation, during descent of the mine to its operating depth, the excess pressure on the lower side of the diaphragm 12 tends to become equalized with the pressure in the upper chamber 19 by flow of air through the bleed duct 34. This flow between the two chambers continues after the mine has reached its operating position and until pressure equilibrium is established.

It will be understood that the interior space within the tail compartment of the mine casing which although occupied in large extent by the various arming components affords sealed air space at substantially atmospheric pr ssure and of large volume compared to that of the Bourdon tube 38. Since the interior of the Bourdon tube is at this pressure, the increased pressure within the chamber 10 causes a counter-clockwise rotation of the arm 39 and, through link 40 and arm 41, a counter-clockwise movement of the contact 24 along the are 36, decreasing its spacing from contact 13 with resultant increase in sensitivity of the pressure device corresponding to the depth.

With equilibrium thus established and sensitivity adjustment made for the present surrounding pressure condition, subsequent relatively slow variation in water depth such as that caused by tides will not effectively operate the contacts because the rate of change in hydrostatic pressure will be slow enough to permit maintenance of sufficient equilibrium between the two chambers through the bleed duct 34 to prevent effective operation of the contacts in response to such change. The consequent slow variation of pressure in the upper chamber 10 will operate through the Bourdon tube regulator to adjust the sensitivity of the device to the changed, water depth.

Any relatively sudden drop in pressure in the near surrounding Water as caused by passage of a ship over the mine will be transmitted to the air within the collapsible chamber ill with negligible variation of pressure within the upper chamber, resulting in a downward deflection of the diaphragm, a downward movement of the stylus 15 and a counter clockwise movement of contact 13. If the drop in pressure is sufficiently great, the contact will engage contact 14 under tension of the spring 18. This connects the control circuit conductors 44-45 to effect energization of the input circuit of the relay system (FIG. 2) which in turn applies power from the battery supply through contacts of relay 46 to power supply conductors leading to the amplifier and sensing device of the mine.

To conserve batteries during stormy weather when high waves cause frequent closure of the control circuit, the relay system is constructed to operate as follows: Closure of connection between conductors 44-45 (FIG. 2) causes current to flow from the plus side of theB- battery over conductors 44-45, through blocking circuit C-R mainly by Way of the condenser as a charging current, thence, through the dropping resistance R and back to minus side of battery via the common r turn conductor 53. The voltage drop across R applied to the control grid of the tube V through R fires the tube, which drawing current through the energizing winding of relay 46 actuates the latter to close its contacts 47- 1% and thereby connect the positive terminals of the B and A batteries to the supply conductors 19 and 50 respectively Conductor 49 now supplies B-battery potential to the blocking circuit to maintain the condenser charged to substantially B-battery potential while conductor 50 supplies power from the A-battery to heating resistor R Heat from K, after a given time say about twenty seconds, causes the thermostatic switch 51 to open the cathode circuit of the tube V thus deenergizing relay 46 to remove battery supply from conductors 49-50 The tube cannot be rendered conducting again until C has partially discharged through R The approximate time required for this delay is 45 seconds. Should the control circuit close before lapse of this period the condenser C of the blocking circuit will be recharged without again causing the tube to conduct. In this event 45 seconds must elapse again before the sensing device and amplifier can be powered to arm the mine. Even in stormy Weather the swells have periods of 15 to 20 seconds so that except for first 20- second period the mine will be unarmed during a period of high waves.

It will be obvious that various operating periods may be obtained by suitable selection of the constants of the relay system. In one embodiment of the invention as here illustrated the operating periods substantially as above set out were obtained through components having the following characteristics:

B, 135 volts V, cold cathode gas tube 359 A C, Z-microfarads R 10,000 ohms R 40 megohms R 100,000 ohms While a specific embodiment of the invention has been herein shown and described for the sake of disclosure, it is to be understood that the invention is not limited to such specific embodiment but contemplates all such modifications and variations thereof as may fall fairly within the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An arming device for electrically controlled mines comprising a control circuit, a pair of chambers having a slow leak pressure equalizing connection between them, one of said chambers having a collapsible wall portion exposed to outside pressure, a pair of normally separated contacts in said circuit, a first pressure responsive means responsive to a drop in pressure in said collapsible wall chamber relative to said other chamber to tend to decrease the distance between said contacts, and a second pressure responsive means tending to decrease the distance between said contacts with increase in pressure in said other chamber.

2. An arming device for electrically controlled mines comprising a casing having a pair of chambers, said chambers having a slow leak passage between them, one of said chambers having a collapsible wall portion exposed to pressure of outside space, a flexible diaphragm connecting the two chambers, a pair of contacts independently movable toward and away from each other, means for transmitting motion from said diaphragm to one of said contacts, a Bourdon tube pressure gauge element in the other of said chambers connected to effect movement of the other contact, a substantially rigid-walled chamber enclosing an air space of large volume relative to the interior volume of the gauge element, and means connecting the interior of the gauge element with said space in sealed relation therewith so that the gauge element will respond to variations in absolute pressure in said other chamber.

3. An arming device for electrically controlled underwater mines comprising a control circuit having a portion normally effectively open, means for effectively closing said circuit portion in response to a drop in pressure of a given amount and within a given rate, electrical actuating means for the mine and a power supply therefor, relay means responsive to said circuit closure to connect the power supply to said actuating means, time delay means actuated upon effective closure of said circuit to open said circuit after a given time, and other time delay means maintaining said efiectively open condition of said circuit for a given period of time.

4. An arming device for electrically controlled underwater mines comprising a control circuit having a portion normally effectively open, means for effectively closing said circuit portion in response to a drop in pressure of a given amount and within a given rate, A and B power buses, electrical actuating means for the mine connected to receive power supply from said buses, sources of A and B power supply, an electrically actuated relay and energizing circuit therefore operable upon energization to connect said A and B sources to said A and B buses, respectively, a cold-cathode gas triode tube connected to draw current through said energizing circuit to energize the relay, a dropping resistance for applying a triggering voltage to the control electrode of the tube, a condenser connected to be charged from said B supply in series with said control circuit and the dropping resistance to trigger the tube, a time delay relay means energized by current from the A bus and operable upon energization to open the tube output circuit after a given time delay, a discharge resistance connected across the terminals of the condenser, said B supply, condenser, discharge resistance and dropping resistance being proportioned as to their electrical constants to prevent subsequent triggering of the tube for a given predetermined time interval.

5. An arming device for underwater mines comprising a source of electrical power, a mine power supply circuit, a normally open control circuit, relay means responsive to closure of said control circuit to connect said power circuit to said source, means responsive to a drop in pressure to close said control circuit, a first timing means operable to open said power circuit after a given time and a second timing means operable upon opening of the power circuit to block operation of the control circuit for a given time.

6. An arming device for electrically controlled underwater mines comprising a control circuit, a pair of normally separated contacts in said circuit, a first pressure responsive means for moving one of said contacts toward the other responsive only to a relatively quick decrease in pressure, a second pressure responsive means for moving said other contact toward said one contact responsive to only a relatively slow increase in pressure.

References Cited UNITED STATES PATENTS 913,524 2/1909 Leon 10217 1,407,633 2/1922 Hammond, Jr 102-17 2,388,459 11/1945 Allen, Jr. 102-16 FOREIGN PATENTS 166,562 7/ 1921 Great Britain 102-70 B 557,110 11/1925 France 102-18 (VI-I, addition to No. 29,013)

BENJAMIN A. BORCHELT, Primary Examiner I. M. HANLEY, Assistant Examiner US. Cl. X.R. 

